A divergence of opinion

Although most models bring the remains of Lorenzo into Ireland and the UK, there’s still a lot of uncertainty about its exact track and how quickly it will fill and dissipate. As expected Met Eireann have now made Lorenzo the first named storm of the season because it will hit them first. It looks like the UKMO will only ever get the opportunity to name a storm if it comes in across the northwest of Scotland, because if it comes in from the west Met Eireann will name it and if it comes in from the southwest Meteo France will nab it too. Interestingly Met Eireann have issued an amber and yellow warning for strong or gale force SE’ly winds that veer W’ly for the whole of Ireland, none of those namby pamby Met Office yellow doughnut shapes for them – I love it.

Meteogroup and the BBC (at 2.30 PM on Wednesday at any rate) are using an unknown NWP model – possibly from the UKMO or ECMWF – that takes Lorenzo southeast across Ireland, across Wales and into central southern England as a rapidly filling feature.

Courtesy of the BBC

This would correspond well with the strong wind warning for SE’ly winds for Northern Ireland issued by the Met Office for Thursday, in which the Met Office expect no more than 60 MPH gusts – as usual with the aforementioned doughnut shape and ridiculous precision they love to employ in all of their warnings these days.

Courtesy of UKMO

The Met Office do have a second warning in force for the extreme southwest of England on Friday that talks of a spell strong westerly winds with maximum gusts of 65 MPH. This kind of ties in with the NWP in the BBC graphics, but on the strength of the gradient you would hardly expect gusts as high as this.

Courtesy of UKMO

All this is fine of course if Lorenzo behaves itself and follows this track and fills rapidly as it does so. Meanwhile the GFS and the ICON model paint quite a different picture. This is the ICON model which takes Lorenzo in a curving arc into western Scotland. This would produce strong or gale force SW’ly winds in Northern Ireland and nothing but a moderate to fresh W’ly over the southwest.

The GFS model arcs the track of Lorenzo a little further north than the UKMO model does, taking Lorenzo across Northern Ireland and then southeast across the Irish Sea and the Midlands and into the continent.

Courtesy of wxcharts.com

I think that the wording of the warnings issued both by the Met Office and Met Eireann highlight the differences in the NWP models they are using. Presumably the Irish are using their own Hirlam model, but who knows what NWP model the BBC are employing, it’s certainly not the GFS, so it’s got to be either the UKMO or ECMWF efforts. I certainly can’t see how the Met Office can justify gusts to 65 knots in the southwest on Friday from this series of charts.

Courtesy of UKMO

Finally, It looks like the NHC have followed the UKMO solution.

Courtesy of NHC

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